In recent years, it has become increasingly apparent that excessive noise produces both short term and long term undesirable effects on those subjected to it. Thus, a high level noise for a short time will increase fatigue and worker irritability, and the long term effects can be partial or total deafness. Recognition of the problem has led to requirements by safety authorities that either call for the reduction of the noise itself, or the provision of protective means such as ear plugs that reduce the effect of the noise.
Any number of different forms of ear plugs have been developed, ranging from the very early use of fibers such as cotton, through soft wax, to various forms of molded plugs formed of materials of varying degrees of hardness. The molded plugs, formed in various shapes, have had various advantages and disadvantages. Aside from the problem of providing sufficient attenuation of the sound, most of the prior plugs have suffered from one or more disadvantages, including ease or difficulty of insertion, adaptability to ear canals of differing size, cleanliness and other problems.
Where the plugs are required by the various safety authorities, it is a real problem for the employer to insure that all of the workers in the noisy areas wear the plugs at all times when they should. If the plugs are not easily installed or are not comfortable, many workers will refuse, or conveniently forget to insert the plugs. In those instances where the worker is working with dirty or abrasive material, wax plugs that must be molded to the ear are quite impractical, since they tend to pick up the dirty or abrasive material and force it into the ear. Additionally, where the employer furnishes the ear plugs, the quantity of plugs that must be furnished is such that cost becomes an important factor.